Three genes related to beta-lactam resistance have been found in the cluster of genes for cephamycin C biosynthesis in Nocardia lactamdurans. The cmcT gene encodes a hydrophobic protein located in the cytoplasmic membrane. The sequence of CMCT has a 21-31% identity in amino acids to proteins involved in antibiotic export from other antibiotic producing microorganisms. The pbp gene encodes a penicillin binding protein. Nocardia lactamdurans is rather sensitive to penicillins, but no to cephalosporins or cephamycin C. A third gene, bla, encodes a type A beta-lactamase. Both the beta-lactamase and the PBP protein, might form a system for the sensing and hydrolysis of penicillin intermediates which are released into the medium during the lysis of antibiotic producing cells.